Unipolar machine.



No. 805,315. PATENTED NOV. 21, 1905. J. E. NOEGGBRATH.

UNIPOLAR MACHINE.

APPLIUATION FILED APR.1, 1905.

Witnesses lnvenLor 23 Q Jakob ENoeg erath UNITED STATES PATENT OFFICE.

JAKOB E. NOEGGERATH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

UNIPOLAR MACHINE.

Specification of Letters Patent.

Patented Nov. 21, 1905.

To all whom, it Ynmy concern.-

Be it known that I, J AKOB E. NOEGGERATH, a citizen of the United States, residing in Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Unipolar Machines, of which the following is a specification.

My invention relates to dynamo-electric machines of the type known as unipolar, and has especial reference to low-voltage machines in which all armature-conductors are dispensed with, and the armature-body itself forms the active material in which the electromotive force of the machine is induced. If. the usual collector-rings are provided for such low-voltage machines in'contact with the body of the armature around its entire periphery, and if a single brush is placed on the collector-ring, it is obvious that the current in the armature-body will tend to flow directly to that part of the collector-ring on whicn the brush bears, so that the distribution of current in the armature-body under the collector-ring will be far from uniform. Since the brush is stationary while the collector-ring and armature-body revolve, the point of maximum current density shifts relative to the armature-body, and this shift ing produces eddy currents, and conse quently losses. This inequality of distribu tion could be to a large extent avoided by distributing brushes around the collectorrings; but in practice such an arrangement would be unsatisfactory, because the brushes at one or both ends of the machine are necessarily inclosed by the field structure and are accessible for purposes of adjustment only through holes provided in the field structure for this purpose. Obviously if the brushes were distributed all around the periphery of the armature it would be exceedingly dilficult to get at them for the purpose of inspection and adjustment, and consequently it is desirable to group the brushes immediately opposite the holes in the field structure.

My invention consists in so arranging the collector-rings that as uniform a distribution is obtained in the armature body with grouped brushes as would be obtained with collector-rings as heretofore arranged and with distributed brushes.

My invention, more specifically stated, consists in arranging the collector-rings so that they are in contact with the armaturebody only at certain points, which are arranged on spiral curves. In this manner a substantially uniform distribution of current on the armature-body under the collectorrings is obtained.

My invention will best be understood by reference to the accompanying drawings, in which Figure 1 shows a side elevation in crosssection, of a unipolar machine provided with collector-rings arranged in accordance with my invention. Fig. 2 shows a detail of one of the collector-rings. Fig. 3 shows a development on a plane surface of the collectorrings and the brushes. Fig. 4 is a diagram of the collector-rings and brushes, and Fig. 5 shows a modified form of the collector-rings.

In Fig. 1 F represents the field structure, provided with a suitable magnetizing-coil and arranged to produce a unipolar fieldfiux. A represents the armature-body, carried on a suitable shaft a. The armature is provided with two sets of collector-rings at opposite ends C and C, on which bear two sets of brushes B and B. The flux may be considered as entering the armature at the central airgap between the two collectorrings, passing axially through the body of the armature toward the left, and returning outwardly into the field structure at the lefthand end of the machine. It will be seen that the brushes B are inclosed by the field structure and are accessible for purposes of inspection and adjustment only through holes in the field structure. Consequently it is desirable that the brushes should be grouped or axially alined directly opposite these holes, one of which is indicated at f. As has been pointed out heretofore, if the collector-rings were in contact with the armature-body around its entire periphery and if the brushes were not distributed the current distribution in the armature-body would not be uniform. In order to secure practically uniform distribution in the armaturebody, I arrange each collector-ring as shown in Fig. 2. The collector-ring has a plurality of inward projections. These projections alone are in contact with the armaturebody. The several collector rings are displaced from each other relative to their inward projections or contact-points, as is shown in the development of Fig. 3. It will be seen that the points of contact of the several rings on the armature body he on spiral curves. This is still more clearly evident from Fig. 4, which shows diagrammatically the connections of the collector-rings. The collectorrings themselves are indicated merely by circles C, while the projections are indicated. by lines 0, connecting the collector-rings to the armature-body A. In this figure each group of brushes is represented by a single brush B, all the brushes being connected collectively to one of the machine-terminals T. It will be seen that this arrangement of the collector rings gives precisely the same distribution of current in the armature-body with grouped brushes that would be obtained it each ring were in contact with the entire periphery of the armature and the brushes were distributed around the entire periphery of the rings.

It is obvious that since the several collector-rings at each end of the machine are electrically connected to each other they can be mechanically in contact with each other as well, so as to form practically one wide colleetor-ring. Thus in Fig. 5 I have shown a development of a single wide collector-ring arranged with spiral projections c. This single ring takes the place of the several rings shown in Fig. 3, the current distribution being substantially the same in both cases. Obviously with the multiple arrangement of rings shown in Fig. 3 the several rings may be relatively interchanged, so that the points of contact do not form an actual spiral. It is suificient it the rings are so arranged that it properly interchanged without shifting any of them peripherally the points of contact would form a spiral. Similarly if the contact-surfaces of the ring shown in Fig. 5 form the equivalent electrically of the spiral projections shown the object of my invention is obtained. Consequently when I use the term spiral in the appended claims I desire to include either an actual spiral or a "potential spiral, as described above. Obviously, also, the projections may be on the armature-body instead of on the rings.

My invention is not limited to the particular arrangement of armature and field structure shown in Fig. I, but is in general applicable to any unipolar machine in which the armature-Indy itself forms the active conducting material of the machine.

hat I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In a dynamo-electric machine, a unipolar field structure, a conducting armaturebody rotatably mounted in said field, collector-rings having portions only in contact with said armature-body, the points 01 contact of said rings being distributed substantially uniformly around the armature, and groups ol collecting-brushes bearing on said rings.

2. In a dynamo-electric machine, a unipolar field structure, a conducting armaturehody'rotatably mounted in said field, collector-rings having portions only in contact with. said armature-body, the points of contact of said rings being arranged in spiral curves on the armaturebody, and axially-alined groups of collecting-brushes bearing on said rings.

' 3. In a dynamo-electric machine, a unipolar field structure, a cylindrical conducting armature-body rotatably mounted in said field, collector-rings having inward. projections in contact with said armature-body, said projections being distributed substantially uniformly around the armature, and groups of collecting-brushes bearing on said rings.

4. In a dynamo-electric machine, a uni polar field structure, a cylindrical conducting armature-body rotatably mounted in said field, collector-rings having inward projections in contact with said armaturebody, said projections being arranged in spiral curves on the armature body, and. axiallyalined groups of collecting-ln'ushes bearing on said rings.

In witness whereof I have hereunto set my hand this 30th day of March, 1905.

JAKOB E. NOEGGERATI'I.

itnesses BENJAMIN B. HULL, I-IELEN ORFORD. 

